Layered heat exchangers

Abstract: A layered heat exchanger for use as a motor vehicle air conditioner evaporator comprises pairs of generally rectangular adjacent plates (2), which are joined together in layers with the corresponding recesses (3) of the plates (2) in each pair opposed to each other to thereby form juxtaposed flat tubes each having a U-shaped fluid channel, and front and rear headers in communication respectively with opposite ends of each flat tube. The turn portion of U-shaped fluid channel of the flat tube has a fluid mixing portion comprising many small projections (12), and a rectifying portion comprising parallel long projections (13) along a flow of fluid. The channel turn portion (3c) rectifies the flow of fluid and mixes the fluid at the same time, permitting the fluid to flow through the turn portion smoothly to result in a diminished fluid pressure loss, an improved heat transfer coefficient and improved performance.

Description: The present invention relates to layered heat exchangers useful as evaporators for motor vehicle air conditioners according to the preamble of claim 1. The FR-A-813972, which is the closest prior art document, discloses an evaporator for motors or similar applications comprising a plurality of radiator elements arranged side by side and being spaced apart. These radiator elements comprise U-shaped flow channels which are provided with vertically elongated rectifying ridges being arranged in parallel on straight channel forming portions of the flow channels to permit a smooth flow of the cooling refrigerant. The US-A 5 111 878 discloses an evaporator for an automotive air conditioner comprising a plurality of tubes arranged side by side. The tubes have a plurality of flow ribs joined in a predetermined pattern therein to form discrete fluid flow sections to improve the heat exchange. The US-A 5 062 477 again discloses an evaporator for an automotive air conditioner consisting of tubes comprising divider ribs to define liquid and vapor passages for the flow of refrigerant around the end in a general U-shaped flow. The US-A 5 125 453 refers to a similar plate-fin heat exchanger having arcuate beads between opposite walls of the tubes of a heat exchanger for directing the fluid flow from the inlet to the outlet portion to improve heat exchange. Already known as such layered heat exchangers are two types; those having headers at one of the upper and lower sides of an assembly of plates in layers, and those having headers at these sides, respectively. Those of the former type have a heat exchange portion which is greater than in the latter type and are therefore expected to exhibit improved performance. Stated more specifically, layered heat exchangers having the header at one side comprise pairs of generally rectangular adjacent plates, each of the plates being formed in one side thereof with a U-shaped channel recess and a pair of header recesses continuous respectively with one end and the other end of the channel recess and each having a fluid passing opening, the plates being joined together in layers with the corresponding recesses of the plates in each pair opposed to each other to thereby form juxtaposed flat tubes each having a U-shaped fluid channel, and front and rear headers communicating respectively with opposite ends of each flat tube for causing a fluid to flow through all the flat tube and the headers. However, the conventional layered heat exchanger having the headers at one side has the problem that when used as an evaporator for motor vehicle air conditioners, the refrigerant fails to flow smoothly along the turn portion of U-shaped channel recess of each plate and to achieve as high an efficiency as is expected. This is because if the plates are designed for example, to produce a rectifying effect, the refrigerant flow pressure loss can be diminished, but a reduced heat transfer coefficient and therefore an impaired heat exchange efficiency will result, whereas if the plates are conversely adapted to give a mixing effect chiefly, the refrigerant flow pressure loss increases to an undesirable level despite an improved heat transfer coefficient. The refrigerant is then liable to stagnate or flow unevenly especially in the vicinity of U-shaped turn portion of the refrigerant channel of each flat tube, consequently permitting the evaporator to exhibit impaired performance. Further with the conventional evaporator, the joint between the plates is made by point contact, which therefore entails the problem that it is difficult to ensure pressure resistant strength. SUMMARY OF THE INVENTION The present invention provides a layered heat exchanger which is free of the foregoing problems. The invention provides a layered heat exchanger according to the claim 1. The turn portion of U-shaped channel forming recess of each plate is provided with a rectifying portion provided at the central part of the turn portion, and the fluid mixing portion at each of front and rear sides of the rectifying portion. The rectifying portion being provided in the central part of the turn portion, the rectifying portion comprises, rearwardly downwardly inclined parallel projections, horizontal parallel projections and forwardly downwardly inclined parallel projections, permitting the fluid to flow from the rear channel portion through the central part of the turn portion and to the front channel portion rapidly. In this case, many small projections are disposed in front of and in the rear of the rectifying portion to provide the fluid mixing portions, where the fluid is fully mixed. With the layered heat exchanger thus constructed, the mixing portion and the rectifying portion provided in the turn portion of U-shaped channel of each flat tube rectify the flow of fluid and mix the fluid at the same time, enabling the fluid to flow through the channel turn portion smoothly to achieve an improved heat transfer coefficient. With the U-shaped channel of the conventional flat tube, the flow of fluid stagnates in the return channel portion upon passing through the turn portion, whereas the flat tube of the invention causes no stagnation, enabling the fluid to smoothly flow in the vicinity of channel turn portion of the tube free of stagnation or flow irregularities. The present flat tube is therefore diminished in fluid pressure loss and can be expected to exhibit greatly improved performance. The small projections for forming the fluid mixing portion and the long projections for constituting the rectifying portion have a height equal to the depth of the recess, or a height which is twice the depth. In the former case, the opposed small projections of the recess turn portions of the adjacent plates as fitted together with their recesses opposed to each other, as well as the opposed long projections, are joined together end-to-end. In the latter case, the small projections and long projections in the recess turn portion are joined at their top ends to the bottom wall of turn portion of the plate opposed thereto. This gives an increased joint area and increases the pressure resistant strength of the heat exchanger. The small projections for the mixing portion in the turn portion of U-shaped fluid channel of each flat tube at the central part thereof, or the long projections for forming the rectifying portion in the central part have a height equal to the depth of the recess. When the adjacent plates are joined to each other, these small or long projections are opposed to each other in corresponding relation, and are joined together end-to-end. The U-shaped channel recess of each plate may have front and rear straight channel forming portions provided with vertically elongated rectifying ridges having a height twice the depth of the recess, each pair of adjacent plates as fitted together having the rectifying ridges arranged alternately in different positions, the rectifying ridges each having an end joined to a bottom wall of the straight channel forming portion of the plate opposed thereto. With this heat exchanger, the elongated rectifying ridges provided on the front and rear channel forming portions of channel recess of each plate permit the fluid to flow straight through the front and rear portions of U-shaped channel of the flat tube, consequently eliminating the likelihood of the fluid pressure loss increasing. Further these elongated rectifying ridges have their top ends joined to the bottom wall of straight channel forming portion of the plate opposed thereto. This results in an increased joint area and imparts enhanced pressure resistant strength to the heat exchanger. The vertically elongated rectifying ridges are arranged alternately in different positions in the assembly of adjacent plates as joined together. The turn portions of the opposed channel recesses have a multiplicity of small projections for forming the fluid mixing portion and long projections for forming the rectifying portion. Accordingly, the elongated rectifying ridges, long projections and small projections on each plate can be smaller in number. The plates can therefore be formed easily. At least one of the adjacent plates in each pair is provided with a U-shaped divided channel forming ridge on the bottom wall of the channel forming recess, the pair of plates being fitted and joined to each other with the corresponding recesses opposed to each other to thereby form a plurality of U-shaped divided independent channels of reduced width inside the flat tube. With the heat exchanger described, the fluid flows through the flat tube without mixing between the adjacent divided channels and free of stagnation. Accordingly, vapor-liquid separation is confined to only one divided channel, therefore diminishes and will not entail an increased fluid pressure loss. The heat exchanger described can be in the following three modes. First, the fluid inlet is provided at one end of the rear header, and the fluid outlet is provided at the other end of the front header, each of the front and rear headers being provided with at least one partition intermediately thereof, the partition being even in total number and arranged on the rear and front sides alternately when seen from above in the direction of from the fluid inlet toward the fluid outlet, to thereby form a zigzag fluid passage divided into an odd number of passageways including an inlet passageway, an outlet passageway and an intermediate passageway between the two passageways, the outlet passageway permitting the fluid to flow therethrough countercurrently against the flow of air. Second, the fluid inlet is provided at one end of the front header, and the fluid outlet is provided at the other end of the front header, each of the front and rear headers being provided with at least one partition intermediately thereof, the partitions being odd in total number and arranged on the front and rear sides alternately when seen from above in the direction of from the fluid inlet toward the fluid outlet, the partitions on the front header being one greater in number than on the rear header, to thereby form a zigzag fluid passage divided into an even number of passageways including an inlet passageway, an outlet passageway and an intermediate passageway between the two passageways, the outlet passageway permitting the fluid to flow therethrough countercurrently against the flow of air. Third, the front header has the fluid inlet at one end thereof, the fluid outlet at the other end thereof and the partition at an intermediate portion thereof to thereby form a zigzag fluid passage divided into an inlet passageway and an outlet passageway, the outlet passageway permitting the fluid to flow therethrough countercurrently against the flow of air. The layered heat exchanger in any of the above modes is useful, for example, as a layered evaporator for use in motor vehicle air conditioners. Since the flow of refrigerant through the outlet passageway is countercurrent against the flow of air, the temperature difference between superheated refrigerant and air to be subjected to heat exchange therewith is greater than in evaporators of the concurrent type wherein the superheated refrigerant is positioned downstream with respect to the direction of flow of air. The portion wherein the refrigerant is in a superheated state therefore achieves a high heat exchange efficiency. Consequently, this portion of the refrigerant passage can be diminished to provide a larger portion for the refrigerant in the form of a vapor and to assure stabilized heat exchange performance. The invention will be described in greater detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic perspective view of a layered heat exchanger of the invention; FIG. 2 is an enlarged fragmentary front view showing a plate of flat tube of the heat exchanger; FIG. 3 is a front view of the plate; FIG. 4 is an enlarged view in section taken along the line 4-4 in FIG. 2; FIG. 5 is an enlarged view in section taken along the line 5-5 in FIG. 2; FIG. 6 is an enlarged fragmentary view in section of the heat exchanger, i.e., the first embodiment; Fig. 7 is an enlarged fragmentary front view showing a plate of flat tube of a heat exchanger as another embodiment of the invention; FIG. 8 is a front view showing a plate for use in another embodiment of the invention before folding; FIG. 9 is a side elevation of the plate; FIG. 10 is an enlarged fragmentary front view showing a plate of flat tube of a heat exchanger as the embodiment of fig. 8; FIG. 11 is a schematic front view of the heat exchanger; DESCRIPTION OF THE PREFERRED EMBODIMENTS Throughout the drawings, like parts are designated by like reference numerals. In this specification, the upstream side of flow of air (i.e., the left-hand side of FIG. 2) will be referred to as "front," the downstream side thereof (i.e., the right-hand side of FIG. 2) as "rear," and the terms "right" and "left" are used for the device as it is seen from the front rearward. FIGS. 1 to 6 show a first embodiment of the invention, i.e., a layered heat exchanger, for use as a layered evaporator 1 in motor vehicle air conditioners. With reference to these drawings, the evaporator 1 comprises pairs of generally rectangular adjacent plates 2 made of aluminum (including an aluminum alloy). Each of the plates 2 is formed in one side thereof with a U-shaped channel recess 3 and two header recesses 4, 4 continuous respectively with the upper-end front and rear portions of the recess 3. The recess 3 is provided with a vertically elongated partition ridge 9 extending centrally of the recess 3 from its upper end to a portion close to the lower end thereof. The ridge 9 has a height nearly equal to the depth of the recess 3. The plates 2 are fitted together in layers with the corresponding recesses 3, 3 and 4, 4 of the plates 2, 2 in each pair opposed to each other, and the opposed partition ridges 9, 9, as well as opposed peripheral edge portions 19, 19, of each pair of plates 2, 2 are joined to each other to thereby form U-shaped flat tubes 5, and a pair of front and rear headers 7, 6 communicating respectively with opposite ends of each flat tube 5. The opposed plates 2, 2 of each two adjacent flat tubes 5, 5 are joined at bottom walls 4a,4a of their header recesses 4, 4 butted against each other and at spacing protrusions 29, 29 formed at the lower ends of the two plates 2, 2 and butting against each other. A corrugated fin 24 is interposed between the flat tubes 5, 5. Side plates 20, 20 are arranged respectively on the right and left outer sides of the evaporator 1 with a corrugated fin 24 also provided between each side plate 20 and the flat tube 5. The side plates 20, 20 and the plates 2 therebetween are each prepared from an aluminum brazing sheet. With reference to FIGS. 2, 3 and 4, the U-shaped channel recess 3 of each plate 2 has front and rear straight channel forming portions 3a, 3b which are provided respectively with vertically elongated rectifying ridges 15, 16. These ridges have a height twice the depth of the recess 3. When the adjacent plates 2, 2 are fitted to each other, these ridges 15, 16 are arranged alternately in different positions. With the pair of plates 2, 2 fitted together, the ridges 15, 16 are positioned in front and rear straight channel portions 5a, 5b of a U-shaped refrigerant channel provided by the flat tube 5, and are arranged symmetically with respect to the central opposed partition ridges 9. More specifically, the front straight channel forming portion 3a of recess 3 of each plate 2 of the present embodiment has two rectifying ridges 15 at widthwise intermediate positions, while the rear straight channel forming portion 3b has three rectifying ridges 16 close to opposite side edges and at widthwise midportion thereof. The plates 2 are identical in shape. When the adjacent plates 2, 2 in each pair are fitted together with their recesses 3, 3 opposed to each other, the front straight channel forming portion 3a of one of the plates. i.e., first plate 2, is opposed to the rear straight channel forming portion 3b of the other plate, i.e., second plate 2, and the rear portion 3b of the first plate 2 is opposed to the front portion 3a of the second plate 2. Thus, the two rectifying ridges 15 of the front portion 3a of the first plate 2 and the three rectifying ridges 16 of the rear portion 3b of the second plate 2, which are five in total number, are arranged alternately, and at the same time, the three ridges 16 of the rear portion 3b of the first plate 2 and the two ridges 15 of the front portion 3a of the second plate 2, which are five in total, are arranged alternately. With the plates 2, 2 in each pair fitted together, these ridges 15, 16 are arranged symmetrically with respect to the central partition ridges 9 of the recesses 3. Further with the two plates 2, 2 fitted together, the top end of each of the ridges 15, 16 is joined to the bottom wall 17 of the straight channel forming portion 3a (3b) of the plate 2 opposed thereto. Next with reference to FIGS. 2, 3 and 5, the U-shaped channel recess 3 of each plate 2 has a turn portion 3c, which is provided with a rectifying portion 11 in the center and refrigerant mixing portions 10, 10 on front and rear sides of the rectifying portion 11. With the present embodiment, the turn portion 3c of U-shaped channel recess 3 of each plate 2 is provided with a multiplicity of small projections 12 for forming the refrigerant mixing portions 10 and long projections 13 for forming the rectifying portion 11. The projections other than those positioned in the center of the turn portion 3c have a height twice the depth of the recess 3. Each pair of adjacent plates 2, 2 as fitted together have the projections with the above-mentioned height arranged alternately in positions different from each other and have the top ends of these small projections 12 and long projections 13 butted against and joined to the bottom wall of the turn portion 3c of the plate 2 opposed thereto. Thus, the U-shaped refrigerant channel of the flat tube 5 has a channel turn portion 5c which is provided with refrigerant mixing portions comprising the multiplicity of small. projections 12, and a rectifying portion comprising the parallel long projections 13. Stated more specifically, the present embodiment had a long projection 13 inclined rearwardly downward and disposed in front of the center of turn portion 3c of recess 3 of each plate 2, a long projection 13 inclined forwardly downward and disposed in the rear of the center at a higher level than the former, and three horizontal long projections 23 and a circular small projection 22. The front half of the turn portion 3c has three small projections 12 disposed at a specified spacing in an oblique arrangement inclined forwardly upward for forming one of the refrigerant mixing portion 10, and the rear half of the turn portion 3c has two small projections 12 spaced apart by a predetermined distance in an oblique arrangement inclined rearwardly upward and a small projection 12 at one side of this arrangement for forming the other mixing portion 10. Further a generally triangular reinforcing projection 14 is provided in the turn portion 3c at a front-half lower corner which will not greatly contribute to heat exchange. The rearwardly downwardly inclined long projection 13 in front of the center of the turn portion 3c, the forwardly downwardly inclined long projection 13 in the rear of the center, the small projection 12 other than the central one 22, and the reinforcing projection 14 have a height twice the depth of the recess 3. The three horizontal long projection 23 and the circular small projection 22 in the central part of the turn portion 3c have a height equal to the depth of the recess 3 like the central partition ridge 9 of the recess 3 and the plate peripheral edge portion 19. When the adjacent first and second plates 2, 2 are fitted together with the recesses 3, 3 opposed to each other, the rearwardly downwardly inclined long projection 13 in front of the center of recess turn portion 3c of the first plate 2 and the forwardly downwardly inclined long projection 13 in the rear of the center of the recess turn portion 3c of the second plate 2 (the latter projection 13 is reversed to opposed the first plate and therefore inclined rearwardly downward) are positioned at different levels, and the top end of each of these long projections 13 is joined to the bottom wall 18 of the turn portion 3c of the plate 2 opposed thereto. The three small projections 12 of the turn portion front half of the first plate recess 3, the upper and lower two small projections 12, 12 in the rearwardly upward oblique arrangement of the turn portion rear half of the second plate 2 and the small projection 12 on the same plate at one side of the arrangement are positioned alternately. The reinforcing projection 14 at the lower front corner of the turn portion 3c of the second plate 2 is positioned opposite to the reinforcing projection 14 of the first plate 2, and is located at the lower rear corner of the second plate turn portion 3c. In the channel turn portion 5c of the U-shaped refrigerant channel of the flat tube 5 provided by the adjacent plates 2 as fitted together, these projections 12 and 14 are symmetric with respect to the center of the channel portion. Further in the assembly of two plates 2, 2, the small projections 12, inclined long projections 13, 13 and reinforcing projection 14 of the turn portion 3c of recess 3 of the first plate 2 are joined each at its top end to the bottom wall 18 of turn portion 3c of the second plate 2 opposed thereto, and the three horizontal long projections 23 and one circular small projection 22 in the center of each turn portion 3c are each joined to the corresponding projection of the other turn portion 3c as butted thereagainst. Consequently, the channel turn portion 5c of U-shaped refrigerant channel of the flat tube 5 is provided with a rectifying portion 11 at its central portion, and a refrigerant mixing portion 10 disposed at each of front and rear sides of the rectifying portion 11 and comprising a multiplicity of small projections 12, the rectifying portion 11 comprising three long projections 23, small projection 22 and inclined long projections 13, 13 in front of and in the rear of these projections. With reference to FIGS. 3 and 6, the front and rear header recesses 4, 4 each have a bottom wall 4a which is formed with a refrigerant passing opening 8 in the form of a circle which is elongated in the front-to-rear direction. The wall 4a has a circular wall 25 surrounding the opening 8 projecting inwardly of the recess 4. With the evaporator 1 described above, a refrigerant introduced into the front header 7 from a refrigerant feed pipe 27 (see FIG. 1) at the right side of the evaporator flows into the flat tubes 5 from the header 7. The refrigerant flows through the U-shaped channel inside each tube 5 into the rear header 6. The front and rear straight channel portions 5a, 5b of the flat tube 5 are provded respectively with the vertically elongated rectifying ridges 15, 16, so that the refrigerant flows straight through these channel portions 5a, 5b without entailing an increased refrigerant pressure loss when flowing through the U-shaped refrigerant channel of the flat tube 5. The channel turn portion 5c of each flat tube 5 has the rectifying portion 11 in its central part and the refrigerant mixing portions 10, 10 on the front and rear sides of the rectifying portion 11. This rectifies the flow of refrigerant and mixes the refrigerant in the channel turn portion 5c at the same time, causing the fluid to flow smoothly through the turn portion 5c to achieve an improved heat transfer coefficient and eliminating stagnation and irregularities from the flow of refrigerant in the vicinity of the channel turn portion 5c for the evaporator to exhibit further improved performance. The refrigerant is discharged from the rear header 6 to the outside via a refrigerant discharge pipe 28 connected to the right end of the header 6. On the other hand, air flows through the clearances accommodating corrugated fins 24 and formed between the adjacent flat tubes 5 of the evaporator 1 and between the tube 5 and the side plate 20 at each end, whereby the refrigerant and air are efficiently subjected to heat exchange through the plates 2 and the corrugated fins 24. It is desired to provide a partition at the bottom of header recess 4 of the plate 2 at a required part of each of the rear and front headers 6, 7 of the evaporator 1 as will be described later so that the refrigerant flows through the evaporator 1 zigzag in its entirety. According to the present embodiment, the ridges 15, 16 of the front and rear straight channel forming portions of the channel recess 3 of each plate 2, and the long projections 13 and small projections of the channel turn portion 3c of the recess 3 have a height twice the depth of the recess 3 and are joined at their top ends to the respective bottom walls 17 and 18 of the plate opposed thereto. The ridges 15, 16, long projections 13 and small projecttions 12 are therefore each joined over an increased area, giving enhanced pressure resistant strength to the evaporator 1. The vertically elongated rectifying ridges 15, 16 of the front and rear straight channel forming portions 3a, 3b of the channel recesses 3 are provided for the front and rear straight channel portions 5a, 5b of refrigerant channel of the flat tube 5 of the adjacent plates 2, 2 as joined together and are positioned symmetrically on the front and rear sides of the channel center line. The turn portions 3c of the opposed recesses 3 have the multiplicity of small projections 12 for forming the refrigerant mixing portions 10 and the long projections 13 for forming the rectifying portion 11, and these projections, except for those positioned centrally of the turn portions 3c, are alternately arranged inside the assembly of adjacent plates 2, 2 and are positioned symmetrically as a whole on the front and rear sides of the turn portion center line. Because of these features, the long rectifying ridges 15, 16, long projections 13 and projections 12 on each plate 2 can be smaller in number. The plate 2 can therefore be formed by facilitated press work. Fig. 7 shows another embodiment of the invention, in which as in the third embodiment, the front and rear straight channel forming portions at opposite sides of the central partition ridge 9 of channel recess 3 of each plate 2 are provided with vertically elongated rectifying ridges 21 which are equidistantly arranged in parallel and which are have a height equal to the depth of the recess 3 (accordingly equal to the height of the ridge 9). Further as is the case with the first embodiment, the turn portion 3c of U-shaped channel recess 3 of each plate 2 has a rectifying portion 11 centrally thereof, and refrigerant mixing portions 10, 10 in front of and in the rear of the portion 11. Although a multiplicity of small projections 12 for forming the mixing portions 10 and long projections 13 for forming the rectifying portion 11 are arranged in substantially the same pattern as in the first embodiment, the small projections 12 of the mixing portion 10 and the long projection 13 of the rectifying portion 11 have a height equal to the depth of the recess 3 (accordingly equal to the height of the partition ridge 9). The channel turn portion 3c has no reinforcing projection at a corner thereof. With the layered evaporator 1 described above which comprises pairs of adjacent plates 2, 2, each pair of adjacent plates 2, 2 are joined together with their recesses 3, 3, as well as the recesses 4, 4, opposed to each other. At this time, the central partition ridges 9 of the channel recesses 3, 3, as well as the vertically elongated rectifying ridges 21 of the straight channel forming portions 3a, 3b, are joined together end-to-end. In the turn portions 3c, 3c of the recesses 3, 3, the opposed small projections 12 of the mixing portions 10, as well as the opposed long projections 13, are joined together end-to-end. Consequently, a U-shaped refrigerant channel of substantially the same shape as in the first embodiment is formed in each flat tube 5 of the evaporator 1. Thus, the channel turn portion 5c rectifies the flow of refrigerant and mixes the refrigerant at the same time when the refrigerant flows three each flat tube 5. The same effect and advantage as in the case of the first embodiment can therefore be expected. FIGS. 8 to 11 show another fifth embodiment of the invention which differs from the embodiment of fig. 7 in respect of the following. This embodiment, i.e., layered evaporator 1, comprises plates 32 having a size corresponding to two plates 2 of the fourth embodiment as interconnected by a joint 33. Flat tubes 5 and front and rear headers 7, 6 communicating with the front and rear ends of U-shaped refrigerant channels of the tubes 5 are formed by folding the plates 32. Each of the upper half 32A and lower halft 32B has a U-shaped channel forming recess 3 including a turn portion 3c, the central part of which has a rectifying portion 11. Refrigerant mixing portions 10, 10 are provided in front of and in the rear of the rectifying portion 11. However, this embodiment has exactly the same construction as the embodiment of fig. 7 with respect to the following. The recess 3 has front and rear straight channel forming portions on the front and rear sides of its central partition ridge 9, and these portions have vertically elongated rectifying ridges 21 which are spaced apart by a distance in parallel and which have a height equal to the depth of the recess 3. A multiplicity of small projections 12 for forming the refrigerant mixing portions 10 and long projections 13 for forming the central rectifying portion 11 are arranged in the same pattern as in the embodiment of fig. 7. The small projections 12 for forming the mixing portion 10 and the long projections 13 for constituting the rectifying portion 11 in the embodiments are not limited in shape to those illustrated but can be shaped otherwise within the scope of the claims.

Claims: A layered heat exchanger comprising pairs of generally rectangular adjacent plates (2), each of the plates being formed in one side thereof with a U-shaped channel recess (3) and a pair of header recesses (4) continuous respectively with one end and the other end of the channel recess (3) and each having a fluid passing opening (8), the plates (2) being joined together in layers with the corresponding recesses (3) of the plates in each pair opposed to each other to thereby form juxtaposed flat tubes (5) each having a U-shaped fluid channel, and front and rear headers (7,6) communicating respectively with opposite ends of each flat tube for causing a fluid to flow through all the flat tubes and headers, the U-shaped channel recess (3) of each plate (2) has a partition ridge (9) at the center portion thereof, vertically elongated rectifying ridges being provided in parallel on straight channel forming portions (3a,3b) disposed on the front and rear sides of the partition ridge (9), the heat exchangers being characterized in that the U-shaped channel recess (3) of each plate (2) having a turn portion (3c) provided with a fluid mixing portion (10) having a multiplicity of small projections (12) and a rectifying portion (11) having parallel straight long projections (13) along a flow of the fluid, said parallel long projections (13) being arranged horizontally, rearwardly downwardly inclined or forwardly downwardly inclined with respect to the flow of the fluid, the channel turn portion (3c) of the U-shaped fluid channel (3) of the flat tube having the rectifying portion (11) centrally thereof and the fluid mixing portion (10) at each of front and rear sides of the rectifying portion (11) with respect to said direction of flow of the fluid, the plates (2) in each pair being joined to each other with their recesses (3) opposed to each other to provide parallel straight fluid channels divided by the rectifying ridges in straight channel portions (5a,5b). A layered heat exchanger as defined in claim 1, characterized in that the multiplicity of small projections (12,22) and the long projections (13,23) provided in the turn portion (3c) of the U-shaped channel recess (3) of each plate have a height equal to the depth of the recess, each pair of adjacent plates (2) as fitted to each other with their recesses opposed to each other having top ends of their opposed small projections and top ends of their opposed long projections butted against and joined to each other, to form the fluid mixing portion of the U-shaped fluid channel turn portion of each flat tube by multiplicity of small projections (12,22) and the rectifying portion (11) of the U-shaped fluid channel turn portion by parallel long projections (13,23). A layered heat exchanger as defined in claim 1, characterized in that the multiplicity of small projections (12,22) and the long projections (13,23) provided in the turn portion (3c) of the U-shaped channel recess (3) of each plate (2) have a height twice the depth of the recess, each pair of adjacent plates as fitted together having the projections with said height arranged alternately in positions different from each other, the small projections and the long projections in the channel recess turn portion (3c) of each pair of adjacent plates each having a top end butting against and joined to a bottom wall of the turn portion of the plate opposed thereto, to form the fluid mixing portion (10) of the U-shaped fluid channel turn portion (3c) of each flat tube (5) by a multiplicity of small projections and the rectifying portion of the U-shaped fluid channel turn portion by parallel long projections. A layered heat exchanger as defined in claim 1, characterized in that the turn portion of the U-shaped channel recess (3) of each plate (2) is formed in its central part with a small projection or long projection having a height equal to the depth of the recess, each pair of adjacent plates (2) as fitted together having the projections with said height arranged alternately in positions different from each other, the small projections (12) or long projections (13) of the channel recess turn portion (3c) of the adjacent plates being joined to each other end-to end, the front and rear small projections or long projections of the channel recess portions each having its top end butted against and joined to a bottom wall of the turn portion of the plate opposed thereto, to form the fluid mixing portion (10) of the U-shaped fluid channel turn portion of each flat tube (5) by a multiplicity of small projections and the rectifying portion of the U-shaped fluid channel turn portion by parallel long projections. A layered heat exchanger a defined in claim 1, characterized in that the center partition ridge (9) of the U-shaped channel recess (3) of each plate (2) has a height same as a depth of the recess (3), the straight channel forming portions (3a,3b) on the front and rear sides of the partition ridge (9) being provided with vertically elongated rectifying ridges (15,16) having a height twice the depth of the recess (3), each pair of adjacent plates as fitted together having the elongated rectifying ridges (15,16) arranged alternately in different positions, and each pair of the adjacent plates being joined to each other with their recesses (3) opposed to each other so that the center partition ridges (9) of the U- shaped channel recesses (3) have top ends thereof abut upon each other, the front and rear straight channel forming portions (3a,3b) of the U-shaped channel recess (3) being provided with the vertically elongated rectifying ridges (15,16) each having an end joined to a bottom wall of the straight channel forming portion of the plate (2) opposed thereto. A layered heat exchanger as defined in claims 1, characterized in that the front and rear straight channel forming portions (3a,3b) of the U-shaped channel recess (3) of each plate (2) is provided with the vertically elongated rectifying ridges (21) having the height same as the depth of the recess (3), the rectifying ridges (21) being arranged in parallel and at regular intervals, each pair of the adjacent plates being joined to each other so that the recesses (3) are opposed to each other and that the center partition ridges (9) of the U-shaped refrigerant channel recesses (3) have top ends thereof abutting upon each other and that the elongated rectifying ridges (21) of the straight channel forming portions (3a,3b) in the front and rear sides of the partition ridges (9) have top end thereof abutting upon each other.

Inventors: GO NOBUAKI, HANAFUSA TATSUYA, NAKAMURA JUMPEI, SHIBATA HIROKI, YAMAZAKI KEIJI, GO, NOBUAKI, HANAFUSA, TATSUYA, NAKAMURA, JUMPEI, SHIBATA, HIROKI, YAMAZAKI, KEIJI
Applicants: SHOWA ALUMINUM CORP, SHOWA ALUMINUM CORPORATION
Application year: 1994
Main classification: F28D1
IPC codes: F28D1, F28F3, F28F27, F25B39